Fix room surfaces, wall openings, and paint scope (#498)

* chore(core): point material catalog at KTX2 tiers for wood/flooring/roofing finishes

All 48 remaining webp/jpg/png finish entries now reference _512.ktx2 maps
and 256px _thumb.webp previews, matching the fabric/leather/concrete/metal
convention. flipY set to false on the converted entries — compressed
textures can't be flipped at upload.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix: stabilize room surfaces and wall openings

* style(core): format KTX2 material catalog

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Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/nodes/src/slab/parametrics.ts

@@ -15,7 +15,7 @@ export const slabParametrics: ParametricDescriptor<SlabNode> = {
   groups: [
     {
       label: 'Elevation',
-      fields: [{ key: 'elevation', kind: 'number', unit: 'm', min: 0.02, max: 1, step: 0.01 }],
+      fields: [{ key: 'elevation', kind: 'number', unit: 'm', min: -1, max: 1, step: 0.01 }],
     },
   ],
   customPanel: () => import('./panel'),